Sleep apnea is one of the most common chronic condition among US military veterans, causing significant detriment to function and quality of life. Persistent daytime symptoms of sleepiness and depression in individuals with obstructive sleep apnea who are using Continuous Positive Airway Pressure (CPAP) are associated with adverse long term medical and functional outcomes. CPAP treatment, while effective at correcting respiratory events and night time blood oxygen saturation levels, does not necessarily improve daytime symptoms, which are responsible for loss of function. We hypothesize that, in individuals with vulnerable circadian system, circadian rhythms disturbances may be triggered by sleep apnea. Our study will be the first to explore the role of Bright Light Therapy (BLT), a well-established non-pharmacological intervention for circadian disturbances, for the treatment of residual daytime symptoms of OSA which do not respond to CPAP. We will recruit 25 Veterans who have been diagnosed with Obstructive Sleep Apnea, are currently adherent to treatment with CPAP and are still experiencing significant symptoms of daytime sleepiness and depression. We will randomize them to receive one of the two possible treatment sequences of Bright Light Therapy (BLT) and sham Bright Light Therapy (s-BLT): BLT-sBLT; sBLT-BLT. We expect patients to experience improvement in sleep related functioning and quality of life during the active treatment portion of the treatment sequence. The results will provide a foundation for a well-powered RCT to test if morning light (bright vs. placebo), as a non- pharmacological adjunctive treatment, can enhance existing treatments for sleep apnea to improve symptom management and functional outcomes.